1. Field of the Invention
The present invention relates generally to systems for completing subterranean wells. In another aspect, the invention concerns a system for perforating, fracturing, and/or packing a multiple-production zone hydrocarbon well with minimal rig time.
2. Description of the Prior Art
After the borehole of a subterranean well has been drilled, casing is typically run into the hole and cemented in place. Before fluid deposits (e.g., oil and/or gas) can be produced from the subterranean formation, the casing must be perforated adjacent a production zone of the formation. Prior to perforating, a high density xe2x80x9ckill-weightxe2x80x9d fluid is typically conducted into the well to produce overbalanced hydrostatic pressure within the wellbore (as compared to the nearby formation fluid pressures). In conventional well perforating operations, the use of such expensive kill-weight fluids is necessary to prevent excessive fluids from prematurely entering the wellbore from the formation.
It is commonly known that when fluids are produced from unconsolidated subterranean formations certain measures must be taken to inhibit the flow of solid particles of the formation into the production tubing. Two common methods of particulate control in subterranean wells include xe2x80x9cgravel packingxe2x80x9d and xe2x80x9cfrac-packing.xe2x80x9d During both gravel packing and frac-packing, a solid particulate material (e.g., 20-80 mesh sand) is placed between the interior of the casing and a screen that is vertically positioned adjacent perforations in the casing. The packing material may also be placed in the perforations extending into the subterranean formation. When the well is completed, the screen fluidly communicates with the production tubing so that fluid produced from the formation must flow through the screen prior to entering the tubing. The solid packing material placed in the annulus between the screen and the casing functions to inhibit the flow of particulates from the formation into the production tubing. Further, the solid packing material may function to help keep the perforations and/or fissures in the subterranean formation from collapsing.
Frac-packing operations combine the features of hydraulic formation fracturing and gravel packing in a single operation. During frac-packing, a mixture of a fracturing fluid (e.g., gelled water, brine, or liquid hydrocarbons) and the solid packing material (typically referred to as a xe2x80x9cproppantxe2x80x9d) are pumped into the subterranean formation under a pressure sufficient to cause the fracturing fluid to enlarge the natural fissures in the formation and/or open up new fissures in the formation. Packers can be positioned in the casing of the wellbore as necessary to direct and control the flow of the frac-packing fluid to the desired portion of the well. During fracturing, the proppant material deposits in the fissures created by the fracturing fluid. After a desired degree of fracturing is achieved, additional proppant material is tightly packed in the annulus between the screen and the casing.
Most conventional techniques for perforating and packing (either gravel packing or frac-packing) a well require the rig to remain over the well while perforating and packing is being performed because the production tubing is typically run in the hole by the rig after perforating and packing. Conventional methods of perforating and packing a well can take several days, or more if multiple production zones are being perforated and packed. In view of the high daily rental rates on rigs (e.g., more than $100,000 per day for many offshore rigs), it would be highly advantageous to be able to set the production tubing and remove the rig from the well prior to perforating and packing the well in order to save rig time. Although it is known in the art that perforating guns can be conveyed into the well on the end of a string of production tubing, such tubing-conveyed perforating systems do not allow multiple production zones to be perforated and packed after the production tubing has been set and the rig has been removed.
It is an object of the present invention to provide a well completion system that consumes less rig time.
Another object of the invention is to provide a well completion assembly that can be maintained in a single fixed position during completion and production of a subterranean well.
Still another object of the present invention is to provide a well completion system that eliminates the need for the use of expensive high density kill-weight completion fluids.
Yet another object of the present invention is to provide a system for perforating and stimulating (i.e., packing, fracturing, or frac-packing) multiple production zones of a subterranean well with minimal time lapse between stimulation of the separate production zones.
It should be noted that the above-listed objects need not all be accomplished by the invention claimed herein, and other objects and advantages of the present invention will be apparent from the written description and appended drawings.
Accordingly, in one embodiment of the present invention, there is provided a well perforating and packing apparatus comprising an elongated porous filter and a perforating gun. The filter extends along a filter axis and has first and second axially spaced filter ends. The perforating gun is axially positioned relative to the filter at least partly between the first and second filter ends. The perforating gun is radially positioned relative to the filter at least partly outside the filter.
In another embodiment of the present invention, there is provided a well completion assembly that is positionable within a cased subterranean wellbore. The well completion assembly comprises an elongated upright member and a perforating gun. The member extends along a member axis and presents a generally cylindrical outer surface. The perforating gun is fixed relative to the member and is axially positioned alongside the member. The perforating gun is operable to propel a plurality of perforating charges outwardly therefrom in a manner such that the perforating charges do not contact the upright member.
In still another embodiment of the present invention, there is provided a completed well operable to produce fluids from a subterranean formation. The completed well comprises a generally upright string of casing, a packer, an elongated upright filter, and a perforating gun. The packer is disposed in the casing and fluidly isolates an upper portion of the casing from a lower portion of the casing. The filter is at least partly disposed in the lower portion of the casing and cooperates with the casing to define a filter annulus therebetween. The perforating gun is at least partly disposed in the filter annulus.
In yet another embodiment of the present invention, there is provided a method of completing a cased well extending in a subterranean formation that holds fluid deposits. The method comprises the steps of: (a) securing a completion assembly comprising an elongated upright conduit and a perforating gun relative to the casing of the well in a fixed position; (b) perforating the casing with the perforating gun while the completion assembly is in the fixed position; (c) packing the well by conveying a packing material downwardly through the conduit while the completion assembly is in the fixed position; and (d) producing fluids from the fluid deposits via the conduit while the completion assembly is in the fixed position.
In yet still another embodiment of the present invention, there is provided a method of completing a cased well extending in a subterranean formation that holds fluid deposits in at least two vertically spaced production zones. The method comprises the steps of: (a) securing a completion assembly comprising an elongated upright conduit, a first perforating gun, and a second perforating gun relative to the casing of the well in a fixed position; (b) perforating the casing in a first vertical location with the first perforating gun while the completion assembly is in the fixed position; and (c) perforating the casing in a second vertical location with the second perforating gun while the completion assembly is in the fixed position.